Project Summary/Abstract There are an estimated 1.6 ? 3.8 million concussion which occur annually in the United States and emergency department visits have doubled in the last decade reflecting either an increased risk or elevated concussion awareness. Concussions have potentially serious complications including second impact syndrome related fatalities, recurrent concussions or other subsequent injuries, and later life neuropathologies. Current clinical assessment batteries are highly sensitive (0.89 ? 0.96) for acute concussion diagnosis; however, practice effects and other limitations preclude the clinical battery from effectively identifying recovery. Thus, accurate assessment of concussion recovery is critically important to ensure safe return to participation and reduce the risk of subsequent neurological, musculoskeletal, or catastrophic injury. A sophisticated postural control assessment battery consisting of single and dual task gait, gait initiation, gait termination, and quiet stance has successfully identified residual impairments post-concussion. Therefore, the first specific aim is to quantify impairments in post-concussion postural control throughout the recovery process and to objectively define the degree of impairment on the day of return to participation. Recent evidence is suggesting an elevated risk of subsequent injury, non-concussion, in the year following concussion; however, the underlying mechanisms have not been elucidated; however, impaired postural control is known predictor of common musculoskeletal injuries. Therefore, the second aim of this proposal is to epidemiologically investigate subsequent post- concussion musculoskeletal injuries and to associate residual impairments in postural control with injury rates. To address these specific aims, we will annually baseline (pre-injury) test 200 student-athletes on the postural control battery and over 600 potential participants have already been tested. We estimate based on previous injury patterns there will be at 40 concussions per year with baseline data available and we will perform regular post-concussion testing on the postural control battery including on the day of return to participation as well as up to 6 months thereafter. We hypothesize there will be clearly evident impairments post-concussion followed by an expected gradual recovery; however, we further hypothesize that residual impairments will persist at return to participation in a subset of the participants. To assess the subsequent injury rates, a prospective cohort design will compare the injury rates following experimental group member?s concussion with a sample large enough to control for gender, sport, and other prior and/or ongoing injury. We hypothesize an elevated risk of post-concussion musculoskeletal injury with the greatest risk in those participants with residual impairments in postural. These findings, if objectively documented, would identify the role of exercise during post-concussion recovery and elucidate a potential underlying mechanism of subsequent injury.